maxon

maxon sensorTechnology – short and to the pointmaxon sensorSensorsmaxon offers a series of sensors. Their characteristicsare:Digital incremental encoder– Relative position signal suitable forpositioning tasks– Rotation direction recognition– Speed information from number of pulses pertime unit– Standard solution for many applicationsDC tachometer– Analog speed signal– Rotation direction recognition– Not suitable for positioning tasksProgram– Digital MILE encoder– Digital MR encoder– Digital Hall effect encoder– Digital optical encoder– DC Tacho– Resolver1 End cap2 Electrical connections motor and encoder3 Print4 MR sensor5 ASIC6 Magnetic multi-pole wheel7 Encoder housing8 Motor connections9 Motor= Solid measure+ Carrier of solid measureResolver– Analog rotor position signal– Analog speed signal– Extensive evaluation electronics required inthe control system– For special solutions in conjunction with sinusoidalcommutation in EC motorsDigital Incremental EncoderMagnetic principlesEncoder signalsFor further processing in the controller, theencoders deliver square-wave signals whosepulses can be counted for exact positioning orspeed measurement. Channels A and B pick upphase shifted signals, which are compared withone another to determine the rotation direction.All maxon positioning systems evaluate therising and falling signal edges. With regard toencoder number of pulses, this results in a fourtimes higher positioning precision. This is what isreferred to as quadcounts.A “home” pulse (index channel I) can be usedas a reference point for precise determination ofrotation angle.The line driver produces complementary signalsA – , B – , Ī which help to eliminate interference onlong signal lines. In addition, this electronicdriver installed in the encoder improves signalquality by steeper signal edges.On the magnetic Encoder a small multipolepermanent magnet sits on the motor shaft. Thechanges in the magnetic flow are recordedby sensors and supplied to the electronics asprocessed channel A and B. Magnetic encodersrequire a minimum of space.MR encoder– Sensor with magnetoresistive principle– Thanks to interpolation, high counts per turnpossible– Different number of pulses can be selected– Index channel possible– Line driver possibleMEnc– Digital Hall sensors– 2 channels A and B– No line driver possible– Low number of pulsesOptical principleIn the optical principle of the fork light barrier(example: HEDL, HEDS, Enc22) an LED sendslight through a finely resolved impulse disc,which is mounted on the motor shaft. The receiver(photo transistor) changes light/dark signalsinto corresponding electrical impulses that areamplified and processed in the electronics.Characteristics– Rather higher space requirement with projectingpart– High number of pulses– Index channel and line driver possible– Very high accuracyInductive principleWith inductive MILE encoders, a high-frequencyalternating field is transformatively transmittedand thus angle dependant modulated, using astructured copper disk.Characteristics– Very robust against magnetic and electricalfields as well as contamination– Very high speeds possible– High precision. Interpolation errors arelargely compensated for by a look-up table– Index channel and line driver available– Absolute interface (SSI) on requestRepresentation of the output signalof a digital encoderSchematic design of amagnetic encoderSchematic design of anopto-electronic encoder90° e Phase shift A,B360° e CycleABIChannel AChannel BChannel IIndex puls widthPhase shift of index pulseNSNS32Technology – short and to the pointMay 2012 edition / subject to change